A scientist designed a foam container to help keep frozen foods from melting. Which best explains how the foam works? It removes
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Complete Question:
Metal sphere A has a charge of − Q . −Q. An identical metal sphere B has a charge of + 2 Q . +2Q. The magnitude of the electric force on sphere B due to sphere A is F . F. The magnitude of the electric force on sphere A due to sphere B must be:
A. 2F
B. F/4
C. F/2
D. F
E. 4F
Answer:
D.
Explanation:
If both spheres can be treated as point charges, they must obey the Coulomb's law, that can be written as follows (in magnitude):
As it can be seen, this force is proportional to the product of the charges, so it must be the same for both charges.
As this force obeys also the Newton's 3rd Law, we conclude that the magnitude of the electric force on sphere A due to sphere B, must be equal to the the magnitude of the force on the sphere B due to the sphere A, i.e., just F.
In a circuit, the electromotive force can be said to be the "source" of the "pushed electrons". This push then creates what is known as a current, which is the flow of electric charge through the circuit. This flow can be slowed down or restricted by a resistor, and this is also what can be harnessed in order to use electric power.
Explanation:
The electromotive force is the potential difference produced by the battery in the circuit. When the circuit is connected to the battery, this potential difference causes the electron to start moving towards the point at higher potential: in this sense, the electromotive force is said to be the "source" of the "pushed electrons".
This flow of electrons moving in the circuit is known as current.
Then, in the circuit, it is possible to place a piece of circuit with a smaller cross-section that restricts the flow of electrons: this component is known as resistor, and its property of restricting the flow of electron is known as resistance.
In a circuit, electromotive force (V), current (I) and resistance (R) are related by Ohm's law:
Finally, when a current passes through a resistor, part of the electric energy is converted into thermal energy, and some power is dissipated through the resistor. The power dissipated is given by
This power can be harnessed, for instance, if the resistor is connected to a light bulb: the energy is transformed into heat and light, and so the light bulb turns on, providing illumination.
Learn more about current and resistance:
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